Here's the alternative you are suggesting: > JWST detects carbon dioxide in planet's atmosphere That's ambiguous. It could be correctly read as "in planet Ear

Here's the alternative you are suggesting: > JWST detects carbon dioxide in planet's atmosphere That's ambiguous. It could be correctly read as "in planet Earth's atmosphere". There isn't anything deceptive about the word "alien", either. It's an alien planet. It's a place that isn't inhabited by us: the original definition of the word.